Tuesday, July 28, 2009

In this post, I would like to throw light upon using RMAN as an alternate method that could be employed to extract controlfiles from RMAN backupsets. This method uses the RMAN command "restore controlfile from '<FULL_PATH_TO_CONTROLFILE_BACKUP>'".

The RMAN method can be used in 3 scenarios. So, make sure that at least any one of the backups is indeed available. Else, you are DOOMED!

I. the controlfile autobackup is turned on in RMAN. In this case the file format would be "c<DBID>-<DATE>-<COUNT>".

Scenario III - Restoring controlfile using RMAN and backupsets (provided backup is taken using the "include current controlfile" clause).

Note: The RMAN backup log would record the backup piece name which includes the controlfile. If you are not sure which backup pice contains the controlfile, then try this on all the backup pieces till the controlfile is restored.

Monday, July 27, 2009

The other day, one of my colleagues posed me this interesting and thought-provoking question/scenario: "Suppose, you were to lose both your production and your RMAN catalog databases irrevertably. You do have a full/incremental RMAN backup, however. How are you going to recover?"

How indeed? I scratched my head and shone a torch upon the dark recesses of my memory to come up with an answer. The light (of the torch) did indeed reveal something - that is that a note existed in Metalink which list the method that could be used to delve into a RMAN backup set to extract the controlfile, the datafiles and also the archivelogs and Voilà, I hit the nail right on the head.

I did some more digging and found a bunch of "Notes" in Metalink that pointed me to the eventual answer to the above question. The Notes that I am referring to are listed below. A summary of the procedure to be followed in such scenarios is also provided. All the notes mentioned use the package dbms_backup_restore.

Scenario:

A successful production backup (RMAN) is available (cold or hot - if hot, then the archivelogs are also available) while the production and the RMAN catalog databases are irrevertably lost.

Assumptions:

1. RMAN is being used to backup the database.

2. The RMAN backup is a "good" backup and is restore and recovery ready.

3. The list of datafiles (file name + full file path) and their datafile numbers is available (this can be obtained from the RMAN backup log file).

Solution Summary (from Note ID: 388057.1):

1. Start the target instance (nomount).

2. Restore the latest controlfile, ideally from the same backupset as the last incremental to be restored (Note 388052.1 : restore controlfile using PLSQL).

3. Make further copies if necessary as per the target database init.ora (pfile).

4. Mount the target instance (alter database mount).

NOTE: (RMAN may be able to be used to restore / recover the database at this point if the controlfile restored knows about the backup required to be restored and recovered).

Wednesday, July 1, 2009

This post is for the automation fanatics and enthusiasts. Of course, the others aren't excluded! The defaultsfile option that can be used with adutilities is a handy option to save time during patching or other maintenance activities.

Though the defaultsfile gets a mention by almost everyone in the context of reducing downtime, the method of creating it is not, unfortunately. In this post, I'd like to share this using an example - compiling apps schema using adadmin.

The above command searches for a file with name adadmin_cmpl_apps_schema.txt in $APPL_TOP/admin/$TWO_TASK directory. If it exists, it uses the values provided in that file. Else, it creates a new file and the contents of the new file would be the answers that one provides at the subsequent prompts of adadmin.

Note: Not mentioning the correct path would error out as below. So, always ensure that you mention the full path to the default file.

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